1. Field of the Invention
The present invention relates to an organic electroluminescence display panel and to a fabrication method thereof.
2. Description of the Related Art
An organic electroluminescence display panel (hereinafter called an ‘organic EL display panel’) includes an organic electroluminescence element (hereinafter called an ‘organic EL element’). In the organic EL element, an organic functional layer made from an organic compound material that affords electroluminescence is interposed between an anode and a cathode. The organic functional layer is a laminate body which can have a variety of configuration. For example, a certain organic functional layer has a three-layer structure, which includes a light emission layer made from an organic compound material affording electroluminescence, a light emission layer and an organic electron transport layer. Another organic functional layer has another three-layer structure which includes an organic positive hole transport layer, a light emission layer and an organic electron transport layer. Still another organic functional layer has a two-layer structure consisting of an organic positive-hole transport layer and a light emission layer. In addition, an electron or positive-hole injection layer and transport block layer may also be inserted between suitable layers among the aforementioned layers.
The organic EL element is supported on a substrate. The substrate is a glass substrates or a resin substrate. One typical resin substrate is a plastic film substrate. The plastic film substrate is flexible so that it is possible to manufacture a flexible display panel.
When exposed to the atmosphere, an organic EL element deteriorates as a result of being affected by moisture, gases such as oxygen and certain types of molecules in the environments. In particular, characteristic deterioration is prominent in organic EL display panels that use a plastic film substrate, i.e., light emission characteristics such as the brightness and hue deteriorate.
In order to prevent such characteristic deterioration, an inorganic barrier film is deposited to a resin substrate. The inorganic barrier film prevents the transmission of moisture and gases such as oxygen. This is gas barrier properties. However, pinholes occur in this inorganic barrier film. These pinholes are sometimes generated as a result of unevenness in the surface of the material where the inorganic barrier film is deposited or the adhesion of foreign matter prior to film deposition. The pinholes may also occur during film deposition. Thus, it is difficult to rid the inorganic barrier film of such pinholes completely. Moisture and gases are able to reach the organic EL element via the pinholes. Consequently, even when an inorganic barrier film is provided on the resin substrate, it is impossible to completely prevent deterioration of the organic EL element.